It's no secret that space exploration generates a lot of waste. Rockets go up, but not everything comes back down, and the standard method for dealing with this has traditionally been to ditch stuff in space or on barren distant worlds, and forget about it.

While the moon's gravity isn't as strong as the Earth's, it still requires a solid amount of thrust in order to get astronauts on their journey back home to Earth, and that means that anything unnecessary for the return flight has to be left behind. In each lunar visit, 20,000 pounds of lunar lander was abandoned on the moon for someone else to worry about later.

A lot of really dumb stuff has been left behind as well - some astronauts, in an effort to spin some additional money out of their experiences, attempted to bring a stack of a hundred $2 bills to and from the moon so that they could sell them at a later date. These were inadvertently left behind, and while on Earth they might be worthwhile, on the moon, they're just standard litter.

There's also golf balls, a portrait of an astronaut, and several sundials that have all been left on the moon simply because they were too much effort to bring back.

Plus, naturally, while astronauts were on the moon, they've needed to continue with their usual bodily functions. There's no sense bringing a big bag of poop back to Earth, so over the course of all the missions to the moon, ninety six bags of human waste were filled and summarily discarded on the lunar surface.

Astronomers are already complaining about "graffiti" that private space companies are leaving in orbit around our planet, and when things really start to heat up in the commercial space sector, there'll be a fight to keep costs down which will inevitably lead to sloppier practices with regards to standard waste.

This is a real shame. The universe is, for the most part, an unspoiled beauty that's free from humanity's frustrating litterbug habits. To see our own careless wastefulness spread out across the stars almost makes it feel as if the universe is better off left unexplored.

There is time before the planet's commercial space companies begin sending up rockets in earnest, and before an inevitable human lunar mission is launched. Let's hope that, by the time this kind of space travel is a reality, the nations of the world will have clubbed together to set a legal framework to prevent us from turning to the moon into just another garbage dump.